Method for Producing and Visualizing an Optically Hidden Mark

ABSTRACT

The utility model can be used to visualize hidden images (marks) that are used to identify the object, thereby providing protection against forgery. The device includes means for cooling of the viewed object (VO), the mirror-like surface (MS) of which includes an optically invisible marking image formed by modifying an area of MS by chaining the surface energy of the modified area. Said optically invisible marking image is characterized by the possibility of visualization through the establishment of a meta-stable environment of water vapor in the area of the MS of the object in the process of cooling VO. A visually perceptible image of the optically invisible mark is obtained in the form of distinguished structures formed by stable phase particles of the meta-stable environment at the sites of the MS of VO having different surface energy. The cooling device contains a designated placement location for VO is embodied in the form of Peltier element realizing the Peltier effect. Contacts and of Peltier element are connected to an electrical circuit with adjustable amperage. The designated placement location is located on the external, visually accessible surface of contact of the cooled Peltier element, enabling the placement of VO in an area with a non-homogenous temperature field and the cooling of MS of VO to a temperature below the dew point temperature of water vapor in the environment surrounding MS by controlled changes in the temperature of the Peltier element cooled contact. The device may be equipped with optical means of visual observation of the visualized marking image.

PERTINENT ART

The invention relates to readout devices for information hidden fromvisual perception and can be mainly used to visualize hidden images ofidentification (marks) of an object, which provide protection againstunauthorized reproduction (forgery), as well as for research purposesfor the visualization of optically invisible structures in the surfacelayer of an object by variation in surface energy values.

PRIOR ART

From the prior art, a method is known for creation and visualization ofoptically invisible marks, according to which the surface area of theprotected object (in particular, jewelry in the form of a diamond), bymeans of a laser beam is formed an image hidden to perception by thenaked eye (the protective label), the subsequent visualization of whichcan be carried out by the use of appropriate optical means (U.S. Pat.No. 4,467,172).

The disadvantages of the known prior art method of visualizing hiddenimages include its limited field of use, For example, in markingjewelry, particularly diamonds, the geometric parameters ofmicrostructures of the protective labels, subject to visualization byoptical means, are so large that they are regarded to be a defect in theproduct, thereby dramatically reducing its aesthetic properties andvalue.

There is also a way of creating and visualizing an optically invisiblemark, according to which an optically invisible marking image is createdon the surface of the object by modifying at least one area of thesurface, followed by visualization of the marking image microstructureby etching and subsequent viewing of the image using the strong opticalor electron microscope (RU, No. 2073270, C1).

The disadvantages of this known prior art method of creating andvisualizing an optically invisible mark, as in the previous case,include the limited field of application because of its applicabilityonly to the special polymer materials in the form of films, as well asthe inability to visualize the latent marking images without the use ofpowerful microscopes.

In addition, the known method does not save the label opticallyinvisible after the first visualization (i.e. visualization by etching).

The closest to the claimed invention is a method of creation andvisualization of an optically invisible mark, according to which thesurface of the object is first polished. On the polished surface, anoptically invisible marking image is formed by modifying at least onearea of the surface. As a result of surface modification, the surfaceenergy of modified sites changes. Said marking image is then visualizedby means of establishing a meta-stable environment in the vicinity ofthe aforementioned surface of the object. By means of said environment,the marking image is produced in the form of distinguished structuresformed by stable phase particles of the meta-stable environment at thesites of the object surface having different surface energy. (WO02/089041, C1, EP 1391841).

The disadvantages of the known method include a relatively low contrastof the visually perceived marking image because of the small differencein the surface energy of modified and un-modified surface areas, andhence the image quality being highly dependent on the investigatedsurface contamination.

Furthermore, during repeat visualization of tags, the marking image maybe overlapped by the image of a structure formed by the merger ofseveral centers of condensation and the emergence of new centers duringevaporation of the condensate from the previous visualization (FIG. 1).That is, the relatively uniform layer of surface contaminationmicro-particles (which are always present in the real worldvisualization) is modified in the event of condensation of droplets onthe surface and evaporation of condensate with the formation of randomlydistributed micro-particle islets on the examined surface. In thesubsequent visualization, these micro-particle islets may becomeadditional functional centers of condensation, distorting the markingimage.

DISCLOSURE OF INVENTION

The basis of the disclosed invention is the task of creating a durable,optically invisible mark (i.e., invisible with the help of any opticalmicroscope), on surface of the object, with high quality visualizedimage, in particular, high contrast and spatial resolution in the realworld environment, with any number of consecutive visualization cyclesby means of increasing the density of condensation centers, which form amark during its visualization, and by reducing the impact of surfacecontamination on the contrast of the viewed image.

The stated task is solved by utilizing a method of creation andvisualization of optically invisible mark, according to which thesurface of the object is first polished and an optically invisiblemarking image is formed on the polished surface by modifying at leastone area of the surface; as a result of said surface modification, thesurface energy of modified sites changes and said marking image is thenvisualized by means of establishing a meta-stable environment in thevicinity of the aforementioned surface of the object; by means of saidenvironment, the marking image is produced in the form of distinguishedstructures formed by stable phase particles of the meta-stableenvironment at the sites of the object surface having different surfaceenergy, whereby, according to the invention, prior to performing eachvisualization process of the optically invisible marking image, thesurface in question, containing the modified areas, is electricallycharged and cleaned by friction.

BRIEF DESCRIPTION OF DRAWINGS

The invention is illustrated by the following graphics.

FIG. 1—the surface of the object with an optically invisible markingimage upon performing the visualization process according to theprototype method.

FIG. 2—the surface of the object with an optically invisible markingimage upon performing the visualization process according to the claimedmethod.

THE BEST EMBODIMENT OF THE INVENTION

The claimed method is embodied as follows.

The surface of the object is first polished. An optically invisiblemarking image is formed on the polished surface by modifying at leastone area of the surface. As a result of said surface modification, i.e.by changing the composition and/or the structure of the near-surfaceatomic layers of the object in question, changes the surface energy ofmodified sites. Concurrently with the changes in surface energy of themodified sites also change the adhesion properties of these sites,being, just as the surface energy, a function of the degree ofdisbalance of surface charges within the surface in question. Saidmarking image is then visualized by means of establishing a meta-stableenvironment in the vicinity of the aforementioned surface of the object.By means of said environment, the marking image is produced in the formof distinguished structures formed by stable phase particles of themeta-stable environment at the sites of the object surface havingdifferent surface energy.

The main characteristic feature of the claimed method is that prior toperforming a visualization process of the optically invisible markingimage, the surface in question, containing the modified areas, iselectrically charged and cleaned by friction.

As a result electrically charging the investigated surface, the excessstatic electricity charge is distributed on this surface in line withthe level of local disbalance of surface charges formed in themodification process. This results in enhanced heterogeneity ofdistribution and increased density of surface charges, which serve ascondensation initiators in the process of visualizing the mark. Thisdecreases the dependence of the visualized image contrast on thecontamination level of the viewed surface.

Electrical charging through friction results in simultaneous cleaning ofthe surface, because, as a result of treatment by friction, themicroparticle islets of impurities formed after evaporation ofcondensate from the previous visualization process, and being additionalfunctional centers of condensation distorting the marking image, areremoved.

Thus, when performing visualization of the surface with modified sitesafter electrically charging and cleaning it by friction increases thecontrast of the image while reducing the dependence of image quality onthe contamination level of the investigated surface.

Supercooled water vapor from ambient air, which is formed when the aircontacts the cooled object in question, is typically used as themetastable environment.

Images of structures, formed by stable phase particles of the metastableenvironment, develop in the form of water droplets on the surface of theobject.

The dynamics of stable phase formation on the surface of the object fromthe metastable environment depends on the free surface energy or themagnitude of adhesion. Within the surface sites with different surfaceenergy, the meta-stable environment converts into stable phase indifferent ways.

The mark is durable because surface modification of an object, causingchanges in its surface energy, obtained, for example, by using spatiallymodulated metals ion beams (e.g. hafnium, chromium), leads to a stable(including at ambient conditions) change in the composition andstructure of the surface with modified surface energy.

An example of a specific embodiment of the claimed method.

A hidden (optically invisible) marking image in the form of inscriptionsand figures was formed on the polished surface of diamond sample bymodifying the surface of the specimen using the ion beam (hafnium ions),passed through a stencil mask. This is followed by electrical chargingand cleaning by friction of the surface in question containing themodified sites. An optical element wiping cloth, enclosed in adielectric frame, was used for electrical charging and cleaning of thesurface. Note that various solvents can be used for cleaning of heavilycontaminated surfaces; however, immediately before the visualization ofthe image, the electrical charging and cleaning of the sample surface iscarried out without using any liquids (by dry friction). Forvisualization of optically invisible image, the sample was put incontact with the cold surface of thermoelectric Peltier element for afew seconds. As a result, water vapor from ambient air condensed on thecooled surface. The optically invisible marking image is visualized inthe form of droplets of water condensate distributed in a specificmanner on the surface of the object, as shown in FIG. 2 of the graphicmaterials, showing the visually perceived marking image formed fromdroplets of water condensate at a 3× magnification.

Tests carried out for one year on the original mark (shown in FIG. 2),revealed no decrease in the image contrast after multiple visualizationduring the test period. Multiple visualization of the marking imageusing metastable medium does not turn the optically invisible markingimage in a permanently visible one, as is the case, for example, in theprototype method after the optically invisible mark in the polymer filmis visualized by the use of alkali etching.

INDUSTRIAL APPLICABILITY

Thus, the claimed invention may find wide application in various fieldsof science and technology for the reading/writing information hiddenfrom visual perception. In particular, it can be used for multiplevisualization of hidden images (marks) that identify an object andprovide protection against unauthorized reproduction (forgery), as wellas for scientific research purposes for visualization of opticallyinvisible structures that vary only in their surface energy levels.

1. A device for the visualization of optically invisible marking images,said device comprising means for cooling of the object, the mirror-likesurface of which includes and optically invisible marking image formedby modifying at least one area of the surface by changing the surfaceenergy of the modified area, said optically invisible marking imagecharacterized by the possibility of being visualized through theestablishment of a meta-stable environment of water vapor in the area ofthe viewed surface of the object in the process of cooling the objectand obtaining a visually perceptible image of the optically invisiblemark in the form of distinguished structures formed by stable phaseparticles of said meta-stable environment at the sites of the objectsurface having different surface energy, and the cooling device beingembodied with a designated placement location for the viewed object,characterized by the device for cooling the object being embodied in theform of Peltier elements realizing the Peltier effect, with the matchedcontacts of said elements being connected to an electrical circuit withadjustable amperage, and the designated placement location on thecooling device being located on the external, visually accessiblecontact surface of the cooled Peltier element, enabling the placement ofthe viewed object in an area with a non-homogenous temperature field andthe cooling of mirrored surface of the object to a temperature below thedew point temperature of water vapor in the environment surrounding theviewed surface by controlled changes in the temperature of the Peltierelement cooled contact.
 2. The device of claim 1, wherein the placementlocation for the viewed object on the cooling device being located in aclosed space, such as a housing, preventing the development ofconvective currents of ambient gas against the cooled surface of theobject, and also being equipped with optical observation devices for thevisualized marking images, including and optical system with aneyepiece, arranged with the ability to display the image by means ofrays of blue and/or white-blue frequency spectrum reflected from thecooled surface of the viewed object, as well as an autonomous source ofdirectional light, such as an LED, generating this range of frequencies.